The Apple Time Capsule is an external hard drive that stores your important documents and media, and can be configured to share specific folders with users on your network. While providing guests with your Time Capsule's password would allow access to all of your storage drive's backed up information, a shared folder has permissions set that enables them to read and write data, or read only depending on your folder's settings.
Click "System Preferences" on your desktop dock or click "Apple" on the menu and click "System Preferences." Click "Sharing" to access the sharing settings.
Click "File Sharing." Click the "+" button to open the search window, which allows you to select the folder to share. Click the Time Capsule icon in the search window, and click the folder you want to share with your guest users.
Click "Choose" and click "+" underneath the Users section and add the user's name and create a password for the user. The user will need this password in order to access the shared folder on Time Capsule.
Click "Read & Write" in the column next to the user's name to change it to read only, or leave the setting to allow the guest to edit the files in the folder.